Numerous impeller pumps are known from the prior art, wherein the impellers are mostly guided mechanically, in some cases also free from bearings. Reference is made to various documents as examples for the field of medical technology:
U.S. Pat. No. 6,116,862 discloses a blood pump with an impeller wheel which is mounted on ball bearings in the axial direction and is centred in the radial direction by a star-shaped cross-member.
EP 0 904 117 B1 discloses a blood pump wherein an impeller is also fixed axially by means of a ball bearing. Radial alignment is provided by means of a friction bearing on a shaft of an impeller or by means of magnets installed on a preliminary housing which is connected to a main housing of the pump by means of a cross-member.
DE 100 16 422 A1 discloses a blood pump which has an impeller fixedly installed in a housing.
In EP 0 599 138 A2 an impeller of a blood pump is arranged on a shaft projecting into a separate housing.
U.S. Pat. No. 5,840,070 discloses a rotor on a shaft wherein alignment is provided by numerous magnets both on impellers of the motor and on the shaft.
DT 26 18 829 A1 discloses a multi-stage centrifugal pump in which the individual pump stages are made of plastic and are deformed by axial pre-stressing wherein side walls of individual stage housings are pressed towards a casing to achieve a tight connection there.
DT 298 21 565 U1 discloses a bearing-free blood pump. An impeller is driven by a magnetic coupling which produces an axial attraction of the impeller to the motor. The impeller can move freely in a pump housing within a limited tolerance and conveys blood in an axial outflow direction when the impeller is driven. The impeller imparts a momentum to the blood to deflect the axially inflowing blood through 90° to a radial outflow. The blades of the impeller have bearing surfaces on their side facing away from the inflow so that the rotating impeller does not make contact axially with the housing as a result of the counter momentum.
U.S. Pat. No. 5,385,581 discloses a blood pump with pure magnetic bearings which support an impeller with an electromagnetic mounting device free from contact. An electronic measuring and control system is provided for this purpose, resulting in a bulky design as a consequence of the complex mounting. In addition, additional energy must be supplied for active centring of the impeller.
Berlin Heart AG has developed an implantable heart support system in the form of an axial pump. This is available on the market under the name INCOR (registered trademark). An impeller rotates in suspension, free from any contact, as a result of a magnetic bearing and takes over the actual pumping function at speeds of up to 12,000 rpm. This corresponds to a possible blood flow of 7 l/min against 150 mmHg. A stationary diffuser wheel positioned after the impeller takes the rotary movement out of the rotating blood, builds up additional pressure and transports the blood to the aorta. The magnets of the axial pump are connected to control electronics for the contact-free mounting of the impeller so that the magnetic field strength can be quickly adapted to a changed position of the impeller over time. The pump has an electrical power consumption of 8.5 W. A running time of about 12 hours is achieved using an external power pack. The object of the invention is to provide a particularly inexpensive, energy-saving and low-wear pump.
With regard to the possible use in medical technology as a blood pump, for example, as a microdiagonal blood pump, the invention additionally relates to further aspects: according to the prior art it is usual for centrifugal pumps to use at least one mechanical friction bearing liable to wear for mounting the impeller. As part of in-vivo studies where these types of blood pumps were tested, problems with the formation of blood clots in the inflow area to the pump were seen again and again. In studies using blood thrombus depositions were found on cross-members for fixing the impeller on an upstream side. With reference to the application in medical technology, it is the object of the invention to provide a blood pump in which thrombus deposition in the inflow area of the pump is reliably avoided with a high degree of reliability using means which can be manufactured very cheaply. At the same time, the pump should be free from wear.